Field of the Invention
The present invention relates to a radiographing apparatus acquiring a radiation image based on a radiation detection signal which is transmitted through an object and detected, and particularly relates to a radiographing apparatus acquiring offset correction data.
Description of the Related Art
A radiation image captured by using radiations such as X-rays is widely used for disease diagnosis and the like. In recent years, a radiation image detector of a flat panel type (FPD) has been used for capturing a radiation image.
The radiation image detector converts radiations which are radiation for a certain accumulation time into an amount of electric charges and accumulates the electric charges in a capacitor. In a case where an electric charge which is unrelated to the radiation of the radiations exists in the radiation image detector at a time of photography, the electric charge is superimposed on the radiation image as noise, and causes deterioration of an image quality of the radiation image. For example, a dark current component due to an electric charge which is generated mainly by an influence of temperature causes noise in the radiation image detector.
In addition, at a time of photographing a radiation image, an electric charge of a dark current component increases in proportion to an accumulation time required for accumulating electric charges, and an image quality of the radiation image is thereby deteriorated. Accordingly, the radiation image detector generates an image (offset image), which is captured during a non-radiation time of radiations, as offset correction data and performs offset correction of the radiation image by using the offset correction data.
In Japanese Patent Laid-Open No. 2003-190126, when a radiation image detector has a plurality of photographing modes, the radiation image detector acquires offset correction data corresponding to each of the photographing modes before capturing a radiation image.
However, in a case where offset correction data is acquired in advance before photography of a radiation image detector, it takes so much time to acquire the offset correction data according to the number of photographing modes, and a waiting time from start of the radiation image detector to the photography becomes long. Moreover, since noise due to an influence of temperature or the like increases over time, update of the offset correction data becomes necessary, so that it takes so much time to update the offset correction data according to the number of photographing modes, and a waiting time from photography of a radiation image to next photography becomes long.